Vehicles, such as vocational and heavy haul trucks, are operable to transport objects (e.g., people, livestock, rubbish, cement, and/or earth materials such as dirt and sand). Such vehicles may comprise a single rate or variable rate suspension.
Single rate suspensions have a fixed spring rate that generally must be set to produce a suspension with either a comfortable ride or a stiff suspension that exhibits adequate roll stability. As a result, either roll stability or ride quality is compromised in a single rate suspension, depending upon the spring rate set for the vehicle.
Variable rate suspensions overcome the deficiency of single rate suspensions by providing multiple spring rates during operation of the vehicle. For instance, as a spring load increases, a spring rate correspondingly increases, and as the spring load decreases, the spring rate correspondingly decreases.
A vocational or heavy haul truck may, for example, achieve a variable rate suspension through the use of bolster springs and auxiliary springs. Alternatively, a vocational or heavy haul truck may, for example, achieve a variable rate suspension through the use of air springs.
Air springs may comprise a bellows that forms at least a portion of an air chamber. A variable spring rate may be achieved by varying the amount of air contained within the air chamber. Although air springs may be used to achieve a variable spring rate, bellows are susceptible to wear and tear that leads to replacement of the bellows and/or air spring.